Answer:
1. The number of rows and columns of the Punnett square is determined by the number of allele combinations an organism produces. For example, for a single trait an organism can produce 2 allele combinations so, there would be 2 rows and 2 columns in a square.
Similarly, in a dihybrid cross or when two traits are considered in a cross, an organism can produce 4 allele combinations. Hence, there will be four rows and four columns in a square.
Maximum number of allele combination an organism can produce is determined by 2ⁿ where n is the number of traits.
Now, Parental genotype: SsBB and ssBb
Number of trait in consideration = 2
So, number of allele combinations = 2² = 4.
Hence, there will be 4 row and 4 columns in the Punnett square.
Gametes produced by SsBB = SB and sB
Gametes produced by ssBb = sB and sb
Punnett square of the cross is shown the figure attached.
2. Total four genotypes were produced:
SsBB, ssBB, SsBb, and ssBb
Each having the ratio of 4/16 = 1/4
3. Two phenotypes were observed:
Thin strips with black eyes (S_B_) and thick strips with black eyes (ssB_).
Each phenotype was found to have the ratio of 8/16 = 1/2 or 50%.
